u can swap the out put shafts u got to remove the drums inside the tranny to get to it why dont you use the s10 tranny it would make things easier

If I may put my 2 cents in here.joshp83 is correct on his advice.. I have an 85 S10 w/SBC, But I couldnt use the original trans only because it had the 2.8 which is a totally different bellhousing pattern...I suggest you get the S10 V8 conversion manual from JTR Publishing ,P.O. Box 66,Livermore,CA., 94551, or order it from summit racing, Im sorry I dont have their part #, but I do have a website for ~~www.V8S10.com~ I highly recommend this manual, it was a huge help even though I bought my truck with the SBC already in it. very useful to show me what I needed to correct the right way ! Good luck & let us know how it turns out.note ~~ the book I got was the 15th printing & published in Jan. 2004. but it should still be relevant for your use